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Abstract The objectives of this work were to evaluate toxicity of certain insecticides including the biocide Bioguard in addition to some chinaberry Fruit extracts against the greater sugar cane borer,sesamia crelica.Changes in the activity of acetylcholinestrase, phenoloxidase and total soluble protein as a result of insecticide treatment were also investigated.The results showed that all tested insecticides resulted in Si~l:;t!~:::r;etductions of S.crelica infestation in maize under open field condition. Such percent reduction was time-dependent for all treatments to reach95% ,93%, 90.9% and 82% after 3 weeks for methoinyl, carbaryl, chlorpyrifos and Bioguard respectively. -Based on LC50values for tested extracts and insecticides against the 3’d instar larvae after 3 days from application of treated artificial diet, methanol extract showed. LC50 value of(6 rng/ L)and was the most effective among tested substances follwed by acetone extract (7mg/ L) .chlorpyrifos (4ImgIL), carbaryl (86mgIL) .rnethomyl (145mg IL ) ,Bioguard (298mg/L), and petrolurn ether extract ( 3349m!!fL ) . -The resalts clearly showed that chloropyrrifos, carbaryl and rnethomyl ;1: LLL) revel caused inhibition of acetylcholinesterase activity and such inhibitory power values were seeming equal and correlated to the toxic effect of tested insecticides. -The results also revealed that all treatments except Bioguard at LC25level caused decreases in protein content.The highest reduction (95% ) of protein was found in methanonl extract - treated 3’d instar larvae. However, Bioguard - treated larvae showed 95% increase in protein content. This may indicate that the mode of action of such extracts are completely different from that of Bioguard . Moreovcr.chinaberry fruit extracts • resulted in elevation of phenoloxidase activity. Methanol extract caused the highest increase (93.6%) in phenoloxidase activity. However, Bioguard caused a great inhibition (72.3%) of the enzyme activity. Such profound effects of these extracts and Bioguard offer an alternative safe substances that can be used through an integrated pest management program for the control of corn borers such as S cretica. |